1. Field of the Invention
The present invention relates to an anti-drowsing device that changes the timing of output of a warning which is output when a collision possibility between an object ahead of a vehicle and the vehicle is detected, and a method therefor.
2. Description of the Related Art
A preceding vehicle proximity warning device is known having a host vehicle speed detection means for detecting the traveling speed of a host vehicle; a preceding vehicle speed detection means for detecting the traveling speed of a preceding vehicle; inter-vehicular distance detection means for detecting the following distance between the host vehicle and the preceding vehicle; a warning generation means for providing a warning to the driver when the speed of the host vehicle relative to the preceding vehicle becomes equal to or higher than a predetermined allowable relative speed depending on the following distance; and a driving state detection means for detecting inattentive driving or drowsy driving of the driver, in which the allowable relative speed is corrected to a lower value when inattentive driving or drowsy driving is detected, so that a warning is provided when the relative speed becomes equal to or higher than the corrected allowable relative speed (for example, see Japanese Patent No. 2583335 (JP-B-2583335)). According to the invention described in Japanese Patent No. 2583335 (JP-B-2583335), when drowsy driving is detected, the allowable relative speed is corrected to a lower value to establish an early-warning mode in which the timing of output of a warning is advanced from that used in a normal mode.
In the invention described in Japanese Patent No. 2583335 (JP-B-2583335), an inattentive state and a drowsy state are dealt with on the same basis, and an early-warning mode is established when an inattentive state or a drowsy state is detected. After that, if the inattentive state or the drowsy state is not detected any longer, the early-warning mode is immediately canceled and the operation is returned to the normal mode.
However, an inattentive state and a drowsy state have naturally different characteristics, and there may be a situation in which the driver is still feeling drowsy and the early-warning mode should be maintained even if a drowsy state is not detected any longer. That is, in general, after a drowsy state has been once detected, the driver may be struggling to keep his or her eyes open against heavy drowsiness even if a drowsy state is not detected any longer. It is therefore desirable to change the timing of output of a warning properly in view of the above point. On the other hand, when the early-warning mode is maintained for a long period after a drowsy state has once been detected, a warning may be output unnecessarily early and disturb the driver.